Television development of communications presentation. Presentation for the lesson "principles of radio communications and television." Reliable radio communication is the key to success

Radio communication is the transmission and reception of information using radio waves propagating in space without wires. Types of radio communications: radiotelegraph, radiotelegraph, radiotelephone and radio broadcasting, radiotelephone and radio broadcasting, television, television, radiolocation. radar.

Radiotelegraph communication is carried out by transmitting a combination of dots and dashes encoding a letter of the alphabet in Morse code. In 1843, American artist Samuel Morse (1791 – 1872) invented the telegraph code. He developed dots and dashes for each letter. When transmitting a message, long signals corresponded to dashes, and short signals corresponded to dots. Morse code is still used today. Radiotelegraph communication is carried out by transmitting a combination of dots and dashes encoding a letter of the alphabet in Morse code. In 1843, American artist Samuel Morse (1791 – 1872) invented the telegraph code. He developed dots and dashes for each letter. When transmitting a message, long signals corresponded to dashes, and short signals corresponded to dots. Morse code is still used today.

Radio broadcasting is the broadcasting of speech, music, and sound effects using e/m waves. Radio broadcasting is the broadcasting of speech, music, and sound effects using e/m waves. Radiotelephone communication involves the transmission of such information only for reception by a specific subscriber. Radiotelephone communication involves the transmission of such information only for reception by a specific subscriber. Radar - detecting objects and determining their coordinates using the reflection of radio waves. Distance from the object to the radar s =сt/2; с – speed of light; t- time interval between t- time interval between pulses pulses

Television Television image transmission is based on three physical processes: Television image transmission is based on three physical processes: Conversion of optical images into electrical signals Conversion of optical images into electrical signals Transmission of electrical signals via communication channels Transmission of electrical signals via communication channels Conversion of transmitted electrical signals into optical imaging Conversion of transmitted electrical signals into optical imaging

To convert the optical image into electrical signals, the phenomenon of the photoelectric effect, studied by A.G., is used. Stoletov. To transmit television signals, radio communications are used, the founder of which was A.S. Popov. The idea of ​​​​reproducing an image on a luminescent screen also belongs to our compatriot B.L. Rosing. Russian engineer-inventor V.K. Zvorykin developed the first transmitting television tube - an iconoscope. To convert the optical image into electrical signals, the phenomenon of the photoelectric effect, studied by A.G., is used. Stoletov. To transmit television signals, radio communications are used, the founder of which was A.S. Popov. The idea of ​​​​reproducing an image on a luminescent screen also belongs to our compatriot B.L. Rosing. Russian engineer-inventor V.K. Zvorykin developed the first transmitting television tube - an iconoscope.

COLOR TELEVISION allows you to transmit and reproduce color images of moving and stationary objects. To do this, in a color television transmitting camera, the image is divided into 3 single-color images. The transmission of each of these images is carried out according to the same principle as in black and white television. As a result, 3 single-color images are simultaneously reproduced on the kinescope screen of a color TV, giving a total color image. The first mechanical type color television system was proposed by the Russian engineer I. A. Adamian.

Invention of radio Popov Alexander Stepanovich () - Russian physicist and electrical engineer, one of the pioneers of the use of electromagnetic waves for practical purposes, inventor of radio.

A report on the possibility of practical use of electromagnetic waves to establish communication without wires was first made on May 7, 1895 by A.S. Popov. This day is considered the birthday of radio. A report on the possibility of practical use of electromagnetic waves to establish communication without wires was first made on May 7, 1895 by A.S. Popov. This day is considered the birthday of radio. On March 24, 1896, at a meeting of the physics department of the Russian Physico-Chemical Society, Popov, using his instruments, clearly demonstrated the transmission of signals over a distance of 250 m, transmitting the world's first two-word radiogram “Heinrich Hertz”. A report on the possibility of practical use of electromagnetic waves to establish communication without wires was first made on May 7, 1895 by A.S. Popov. This day is considered the birthday of radio. A report on the possibility of practical use of electromagnetic waves to establish communication without wires was first made on May 7, 1895 by A.S. Popov. This day is considered the birthday of radio. On March 24, 1896, at a meeting of the physics department of the Russian Physico-Chemical Society, Popov, using his instruments, clearly demonstrated the transmission of signals over a distance of 250 m, transmitting the world's first two-word radiogram “Heinrich Hertz”.

In the antenna, under the influence of an alternating electric field, forced oscillations of free electrons arose with a frequency equal to the frequency of the electromagnetic wave. Alternating voltage from the antenna was supplied to the coherer - a glass tube filled with metal filings. Under the influence of high-frequency alternating voltage, electrical discharges occur in the coherer between individual sawdust, and its resistance decreases several times. In the antenna, under the influence of an alternating electric field, forced oscillations of free electrons arose with a frequency equal to the frequency of the electromagnetic wave. Alternating voltage from the antenna was supplied to the coherer - a glass tube filled with metal filings. Under the influence of high-frequency alternating voltage, electrical discharges occur in the coherer between individual sawdust, and its resistance decreases several times.

The current in the coil of the electromagnetic relay increases, and the relay turns on the electric bell. This is how the reception of the e/m wave by the antenna was recorded. Hammer el. The bell, hitting the coherer, shook the sawdust and returned it to its original position - the receiver was again ready to register e/m waves. The current in the coil of the electromagnetic relay increases, and the relay turns on the electric bell. This is how the reception of the e/m wave by the antenna was recorded. Hammer el. The bell, hitting the coherer, shook the sawdust and returned it to its original position - the receiver was again ready to register e/m waves.

Somewhat later, the Italian physicist and engineer G. Marconi created similar devices and conducted experiments with them. In 1897 he received a patent for the use of electromagnetic waves for wireless communications. Thanks to large material resources and energy, Marconi, who had no special education, achieved widespread use of the new method of communication. In 1897 he received a patent for the use of electromagnetic waves for wireless communications. Thanks to large material resources and energy, Marconi, who had no special education, achieved widespread use of the new method of communication. Popov did not patent his discovery. Popov did not patent his discovery.

Increasing the communication range At the beginning of 1897, Popov established radio communication between the shore and the ship, and in 1898, the radio communication range between ships was increased to 11 km. A great victory for Popov and the barely emerging radio communications was the rescue of 27 fishermen from a broken ice floe that was carried out to sea. The radiogram transmitted over a distance of 44 km allowed the icebreaker to go to sea in a timely manner. Popov's works were awarded a gold medal at the 1900 World Exhibition in Paris. In 1901, on the Black Sea, Popov in his experiments reached a range of 148 km.

By this time, a radio industry already existed in Europe. Popov's work was not developed in Russia. Russia's lag in this area was growing alarmingly. And when in 1905, in connection with the outbreak of the Russian-Japanese War, a large number of radio stations were needed, there was nothing left to do but order them from foreign companies.

Popov's relations with the leadership of the naval department worsened, and in 1901 he moved to St. Petersburg, where he was a professor and then the first elected director of the Electrotechnical Institute. The worries associated with fulfilling the responsible duties of the director completely undermined Popov’s health, and he died suddenly of a cerebral hemorrhage.

Even after gaining great fame, Popov retained all the main traits of his character: modesty, attention to other people’s opinions, willingness to meet everyone halfway and help those in need of help as much as possible. When work on the use of radio communications on ships attracted the attention of foreign business circles, Popov received a number of offers to move to work abroad. He resolutely rejected them. Here are his words: “I am proud that I was born Russian. And if not my contemporaries, then perhaps our descendants will understand how great my devotion to our Motherland is and how happy I am that a new means of communication has been discovered not abroad, but in Russia.”

The master oscillator produces high-frequency harmonic oscillations (carrier frequency more than 100 thousand Hz). The master oscillator produces high-frequency harmonic oscillations (carrier frequency more than 100 thousand Hz). The microphone converts mechanical sound vibrations into electrical vibrations of the same frequency. The microphone converts mechanical sound vibrations into electrical vibrations of the same frequency. A modulator changes the frequency or amplitude of high-frequency oscillations using low-frequency electrical oscillations. A modulator changes the frequency or amplitude of high-frequency oscillations using low-frequency electrical oscillations. High- and low-frequency amplifiers enhance the power of high-frequency and sound (low-frequency) vibrations. High- and low-frequency amplifiers enhance the power of high-frequency and sound (low-frequency) vibrations. The transmitting antenna emits modulated electromagnetic waves. The transmitting antenna emits modulated electromagnetic waves.

The receiving antenna receives e/m waves. An electromagnetic wave that reaches the receiving antenna induces in it an alternating current of the same frequency at which the transmitter operates. The receiving antenna receives e/m waves. An electromagnetic wave that reaches the receiving antenna induces in it an alternating current of the same frequency at which the transmitter operates. The detector selects low-frequency oscillations from modulated oscillations. The detector selects low-frequency oscillations from modulated oscillations. The speaker converts e/m vibrations into mechanical sound vibrations. The speaker converts e/m vibrations into mechanical sound vibrations.

Modulation of a transmitted signal is a coded change in one of its parameters. Modulation of a transmitted signal is a coded change in one of its parameters. In radio engineering, amplitude, frequency and phase modulation are used. In radio engineering, amplitude, frequency and phase modulation are used. Amplitude modulation is a change in the amplitude of oscillations of a high (carrier) frequency by oscillations of a low (sound) frequency. Amplitude modulation is a change in the amplitude of oscillations of a high (carrier) frequency by oscillations of a low (sound) frequency. Detection (demodulation) - separation of high-frequency audio signals from modulated oscillations. Detection is carried out by a device containing an element with one-way conductivity: a vacuum or conductor diode detector. Detection (demodulation) - separation of high-frequency audio signals from modulated oscillations. Detection is carried out by a device containing an element with one-way conductivity: a vacuum or conductor diode detector.

Propagation of radio waves RADIO WAVES, electromagnetic waves with a frequency less than 6000 GHz (with a wavelength λ greater than 100 μm). Radio waves with different λ differ in the characteristics of their propagation in near-Earth space and in the methods of generation, amplification and radiation. They are divided into extra-long (λ > 10 km), long (10-1 km), medium (m), short (m), VHF (λ 10 km), long (10-1 km), medium (1000-100 m ), short (100-10 m), VHF (λ

Propagation of radio waves The ionosphere is the ionized upper part of the atmosphere, starting at a distance of about km from the earth's surface and passing into interplanetary plasma. The ionosphere is capable of absorbing and reflecting electromagnetic waves. Long and short waves are reflected well from it. The ionosphere is the ionized upper part of the atmosphere, starting at a distance of about km from the earth's surface and turning into interplanetary plasma. The ionosphere is capable of absorbing and reflecting electromagnetic waves. Long and short waves are reflected well from it. Long waves are able to bend around the convex surface of the Earth. Due to multiple reflections from the ionosphere, radio communication on short waves is possible between any points on Earth. Long waves are able to bend around the convex surface of the Earth. Due to multiple reflections from the ionosphere, radio communication on short waves is possible between any points on Earth. VHFs are not reflected by the ionosphere and pass freely through it; They do not go around the surface of the Earth, so they provide radio communication only within line of sight. Television broadcasting is only possible in this frequency range. To expand the reception area of ​​television broadcasts, transmitter antennas are installed at the highest possible height; for the same purpose, repeaters are used - special stations that receive signals, amplify them and radiate them further. VHF is capable of providing communication through satellites, as well as communication with spacecraft. VHFs are not reflected by the ionosphere and pass freely through it; They do not go around the Earth's surface, so they provide radio communication only within line of sight. Television broadcasting is only possible in this frequency range. To expand the reception area of ​​television broadcasts, transmitter antennas are installed at the highest possible height; for the same purpose, repeaters are used - special stations that receive signals, amplify them and radiate them further. VHF is capable of providing communication through satellites, as well as communication with spacecraft.

Space communications Communication satellites are used to relay television programs throughout the country and for mobile telephone communications. The satellite receives signals and sends them to another ground station located several thousand kilometers away from the first one. Signals from a communications satellite received by a ground station are amplified and sent to receivers of other stations. Communication satellites are used to relay television programs throughout the country and for mobile telephone communications. The satellite receives signals and sends them to another ground station located several thousand kilometers away from the first one. Signals from a communications satellite received by a ground station are amplified and sent to receivers of other stations.

Radar Christian Hülsmeier, living in Düsseldorf, invented the radar. The birthday of the invention can be considered April 30, 1904, when Hülsmeier received a certificate for his invention from the Imperial Patent Office. And on May 18, the radar was tested for the first time on the Cologne railway bridge... Christian Hülsmeier, living in Düsseldorf, invented the radar. The birthday of the invention can be considered April 30, 1904, when Hülsmeier received a certificate for his invention from the Imperial Patent Office. And on May 18, the radar was tested for the first time on the Cologne railway bridge... Christian Hülsmeier Christian Hülsmeier Radar, or radar, sends out a directed beam of radio waves. A car, plane or any other large metal object encountered in the path of a radio beam reflects it like a mirror. The radar receiver picks up the reflection and measures the time it takes for the pulse to travel to the reflecting object and back. Using this time, the distance to the object is calculated. Scientists use radars to measure the distance to other planets, meteorologists to identify thunderstorm fronts and predict the weather, and traffic inspectors to determine the speed of a car. Radar, or radar, sends out a directed beam of radio waves. A car, plane or any other large metal object encountered in the path of a radio beam reflects it like a mirror. The radar receiver picks up the reflection and measures the time it takes for the pulse to travel to the reflecting object and back. Using this time, the distance to the object is calculated. Scientists use radars to measure the distance to other planets, meteorologists to identify thunderstorm fronts and predict the weather, and traffic inspectors to determine the speed of a car.

Emergency radio rescue service This is a set of artificial satellites moving in circular circumpolar orbits, ground-based information receiving points and radio beacons installed on aircraft, ships, and also carried by climbers. In the event of an accident, the beacon sends a signal that is received by one of the satellites. A computer located on it calculates the coordinates of the radio beacon and transmits information to ground points. The system was created in Russia (COSPAS) and the USA, Canada, France (SARKAT). This is a set of artificial satellites moving in circular circumpolar orbits, ground-based information receiving points and radio beacons installed on aircraft, ships, and also carried by climbers. In the event of an accident, the beacon sends a signal that is received by one of the satellites. A computer located on it calculates the coordinates of the radio beacon and transmits information to ground points. The system was created in Russia (COSPAS) and the USA, Canada, France (SARKAT).

Message topics: Life and work of A.S. Popova Life and work of A.S. Popova History of the invention of television History of the invention of television Main directions of development of communications Main directions of development of communications Human health and cell phone Human health and cell phone Radio astronomy Radio astronomy Color television Color television History of the creation of the telegraph, telephone History of the creation of the telegraph, telephone Internet (history of creation) Internet( History of creation)

• Radio communication – transmission and reception of information using radio waves propagating in space without wires.

Radar

Radiotelephone

Types of radio communication

Radiotelegraph

Broadcasting

A television

• Popov Alexander Stepanovich, Russian physicist and electrical engineer, inventor of electrical communication without wires (radio communications, radio). In 1882 he graduated from the Faculty of Physics and Mathematics of St. Petersburg University and was left there to prepare for scientific work.

• Popov's first scientific research was devoted to the analysis of the most beneficial action of dynamoelectric machines (1883) and induction balances Yuza (1884). After the publication (1888) of G.’s works. Hertz in electrodynamics, Popov began to study electromagnetic phenomena and gave a series of public lectures on the topic “The latest research on the relationship between light and electrical phenomena.” Trying to find a way to effectively demonstrate Hertz's experiments to a large audience, Popov set about constructing a more visual indicator of electromagnetic waves (EMWs) emitted Hertz vibrator .

To produce electromagnetic waves, Heinrich Hertz used a simple device called a Hertz vibrator. This device is an open oscillatory circuit.

• Radio receiver circuit
• A. S. Popova:
• M and N- holders to which the coherer is suspended by means of a light clock spring;
• A and B- platinum coherer plates, to which the voltage of the electric battery (P-Q) is constantly supplied through a polarized relay (Relay).

Principle radio communications is is that it was created high frequency electric current , created in the transmitting antenna, causes in the surrounding space rapidly changing electromagnetic field , which distributed by as electromagnetic wave .

Basic principles of radio communication

Receiving circuit

speaker

Before. antenna

Reception. antenna

Basic principles of radio communication. Block - diagram.

Master oscillator (GHF) produces harmonic HF oscillations.

Microphone converts mechanical sound vibrations into electrical vibrations of the same frequency.

Modulator changes (modulates) the frequency or amplitude of HF oscillations with the help of electrical oscillations of low LF frequencies.

High and low frequency amplifiers UHF and ULF enhance the power of high-frequency and low-frequency electrical vibrations.

Transmitting antenna emits modulated electromagnetic waves.

Receiving antenna receives electromagnetic waves. An electromagnetic wave, reaching the receiving antenna, induces in it an alternating current of the same frequency at which the transmitter operates.

Detector selects low-frequency oscillations from modulated high-frequency oscillations.

Speaker converts electromagnetic vibrations into mechanical sound vibrations.

• In 1899, P. N. Rybkin and D. S. Troitsky, Popov’s assistants, discovered the coherer detector effect. Based on this effect, Popov built a “telephone dispatch receiver” for auditory reception of radio signals (on headphones) and patented it (Russian privilege No. 6066 of 1901). Receivers of this type were produced in 1899-1904 in Russia and France (Ducretet company) and were widely used for radio communications. At the beginning of 1900, Popov’s devices were used for communication during the work to eliminate the accident of the battleship “General-Admiral Apraksin” off the island of Gogland and during the rescue of fishermen carried away on an ice floe at sea. At the same time, the communication range reached 45 km. In 1901, Popov, in real ship conditions, obtained a communication range of 148-150 km.

• When work on the use of radio communications on ships attracted the attention of foreign business circles, Popov received a number of offers to move to work abroad. He resolutely rejected them. Here are his words:
• « I am proud that I was born Russian. And if not my contemporaries, then perhaps our descendants will understand how great my devotion to our homeland is and how happy I am that a new means of communication has been discovered not abroad, but in Russia ».

Radar - detection of objects and determination of their coordinates using the reflection of radio waves.

Radars are used to determine the distance and detect aircraft, ships, cloud accumulations, planetary locations, and in space research. Using radar, the speed of the orbital motion of the planets, as well as the speed of their rotation around their axis, is determined.

Lesson 2/1
Radio Basics
Study questions
1. Classification of radio waves.
2. Propagation of radio waves of various ranges.

Literature

Krukhmalev
IN.
AND.
And
etc.
Basics
construction
telecommunication systems and networks. Textbook. HotlineTelecom, M.: 2008. 2000у.
2. Motorkin V.A. and others. Practical foundations of radio communication. Educational
allowance. Khimki, FGOU VPO AGZ EMERCOM of Russia, 2011. 2476k.
3. Papkov S.V. and others. Terms and definitions of communication in the Ministry of Emergency Situations of Russia. –
Novogorsk: AGZ. 2011. 2871k.
4. Motorkin V.A. etc. A course of lectures on the discipline (specialty
– protection in emergencies) “Communication and warning systems” (textbook) –
Khimki: AGZ EMERCOM of Russia - 2011. 2673k.
Golovin O.V. and others. Radio communication - M.: Hotline - Telecom,
2003. pp. 47-60.
Nosov M.V. Radio communication systems - N.: AGZ, 1997.
Papkov S.V., Alekseenko M.V. Basics of organizing radio communications
in RSChS - N.: AGZ, 2003. P. 3-10.
1.
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2

1st study question
Classification of radio waves
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3

300
m
f MHz
Wave Range - Frequency Range
Power frequency EM waves
Radio band:
Extra-long (ULF) – Ultra-low (ELF)
Long (LW) – Low (LF)
Middle (MW) – Middle (Mid)
Short (HF) – High (HF)
Ultra short (VHF): Very high (VHF),
Ultra high (UHF),
Ultra high (microwave)
Millimeter (MMW)
Decimillimeter (DMMV)
Optical range:
Infrared rays
Visible light
Ultra-violet rays
300
f MHz
m
Wavelength (m)
-105
Frequency (MHz)
(0-3) 10-3
105-104
104-103
103-102
102-101
101-100
100-10-1
10-1-10-2
10-2-10-3
10-3-10-4
(3-30) 10-3
(3-30) 10-2
(3-30)-1
(3-30)0
(3-30)1
(3-30) 102
(3-30) 103
(3-30) 104
(3-30) 105
3.5 10-4-7.5 10-7
7.5 10-7-4 10-7
4 10-7-5 10-9
8.6 106-4 108
4 108-7.5 108
7.5 108-6 1010
X-rays
10-8-10-12
3 1010-3 1012
- rays
10-12-10-22
3 1012-3 1024
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6

Type of radio waves
Type of radio waves
Range
radio waves
(wavelength)
Myriameter
Extra long
(ADV)
10...100 km
4
3...30 kHz
Very low
(VLF)
Kilometer
Long (LW)
1...10 km
5
30...300 kHz
Low (LF)
Hectometric
Medium (SV)
100…1000 m
6
300...3000 kHz
Mids (mids)
Decameter
Short (HF)
10...100 m
7
3...30 MHz
Treble (HF)
Meter
1...10 m
8
30...300 MHz
Very high
(VHF)
decimeter
10...100 cm
9
300...3000 MHz
Ultra high
(UHF)
1...10 cm
10
3...30 GHz
Extra high
(microwave)
Millimeter
1...10 mm
11
30...300 GHz
Extremely high
(EHF)
decimmillimeter
e
0.1...1 mm
12
300...3000 GHz
Hyperhigh (HHF)
Centimeter
Ultra short
(VHF)
№
range
on
Range
frequencies
Type of radio frequencies

2nd study question
Propagation of radio waves of various ranges
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8

Types of radio wave propagation:
along the earth's surface;
with radiation into the upper layers of the atmosphere and from them back to
surface of the Earth;
with reception from Earth and return transmission to Earth via
space relays.
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Rice. Ideal radio wave propagation
9

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Rice. Radio wave propagation paths

Type of radio waves
Basic methods
distribution
radio waves
Communication range, km
Myriameter and
kilometer
(extra long and
long)
Diffraction. Reflection
from the Earth and the ionosphere
Up to a thousand. Thousands
Hectometric
(average)
Diffraction.
Refraction in
ionosphere
Hundreds. Thousands
Decameter
(short)
Refraction in
ionosphere and reflection
from the earth
Thousands
Meter and more
short
Free
distribution and
reflection from the Earth.
Troposphere scattering
Dozens. Hundreds

Peculiarities of propagation of waves in the MF, LF and VLF ranges
Waves with lengths from 1 to 10 km, low frequency range, and even longer ones,
exceed the size of soil unevenness and obstacles, and when
propagation, diffraction is noticeably manifested (bending around the earth's surface,
etc).
The waves then propagate in free space rectilinearly,
the formation of a “dead zone” is possible. As the frequency decreases, energy loss
waves decrease when absorbed by the soil. Therefore, LF and VLF with the same
Radiation powers travel over longer distances than short ones.
At a power of tens of kW, the field strength of surface waves
sufficient to receive signals over distances of thousands of kilometers.
Spatial waves of these ranges, when propagating in
direction of the ionosphere, are reflected and return to the Earth. Happening here
reflection from the earth's surface, etc. This distribution is called
multi-hop.
Long-distance ionospheric wave propagation has negative consequences for radio communications.
consequences if superficial and
spatial waves - multipath. At point B, addition occurs
waves - interference.
VLF waves have the ability to penetrate a wide range of
depth into the surface layer of the earth and even into sea water. It does
02/03/2017 VLF communications with underground and underwater objects. 14
possible

Type of radio waves
Basic methods
radio wave propagation
Communication range, km
Myriameter and
kilometer (extra-long
and long)
Diffraction. Reflection from
Earth and ionosphere
Up to a thousand. Thousands
Hectometric (average)
Diffraction. Refraction in
ionosphere
Hundreds. Thousands
Decameter (short)
Refraction in the ionosphere and
reflection from the Earth
Thousands
Meter and shorter
Free distribution and
reflection from the Earth.
Troposphere scattering
Dozens. Hundreds

Losses in the soil increase with increasing frequency, the radio communication range with
using surface waves in the MF is less than in the LF (1500 km).
Spatial waves are strongly absorbed in the ionosphere during the day, and at night
radio reception at distances of 2-3 thousand km. Between the radio reception area
surface waves, and a more distant reception area of ​​spatial waves
there is a territory in which the intensity of both waves has
same order of magnitude. Therefore, deep interference is possible
fading and radio communication turns out to be unstable.
HF Wave Propagation
Due to significant energy losses in the soil, long-distance communication by surface
waves in the HF range rarely exceed 100 km. Ionospheric propagation
waves, improves with increasing frequency due to reduced losses.
The reflection of waves from a smooth surface turns out to be specular: angle
incidence is equal to the angle of reflection. The ionosphere is heterogeneous and uneven, therefore
waves are reflected in different directions, i.e. scattered
reflection. In Fig. this property of reflected waves forming is shown
relatively wide beam 1. Between the surface propagation zone
waves and the territory into which spatial waves arrive is formed
“dead zone” Some of the wave energy may not be reflected to the Earth at all, but
propagates in the layer as in a conductor (the trajectory is designated 2). If the waves
experience insufficient refraction in the ionized layer, then they go into
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17
transatmospheric
space; This case corresponds to trajectory 3.

Rice. Path of radio waves in the ionosphere
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Rice. Addition of radio waves due to multipath propagation
19

Type of radio waves
Basic methods
radio wave propagation
Communication range, km
Myriameter and
kilometer (extra-long
and long)
Diffraction. Reflection from
Earth and ionosphere
Up to a thousand. Thousands
Hectometric (average)
Diffraction. Refraction in
ionosphere
Hundreds. Thousands
Decameter (short)
Refraction in the ionosphere and
reflection from the Earth
Thousands
Meter and shorter
Free distribution and
reflection from the Earth.
Absorption. Scattering in
troposphere
Dozens. Hundreds

Propagation of VHF, UHF and Microwave Bands
Microwave waves travel like light
straight forward. Diffraction in these ranges is weak. Waves emitted under
angle to the earth's surface, go into the extra-atmospheric space almost
without changing the trajectory, this property made it possible to successfully apply
microwaves for satellite communications.
The inability of waves in these ranges to bend around the surface requires
radio communications ensuring geometric visibility between the transmitting and
receiving antennas (Fig. a, b).
Since the waves are reflected from the earth's surface, at the point of reception
interference of beams is possible (Fig. c); and interference arises
fading and distortion of transmitted messages.
At relatively high power, the communication range is significantly
exceeds normal. Unevenness of the earth's surface and differences in soils,
vegetation cover, the presence of rivers and reservoirs, settlements, engineering
structures, etc. affect the lower layers of air, leading to the formation of
atmosphere of zones with different temperatures and humidity, local flows
air, etc. In these zones, at altitudes up to several kilometers, occurs
wave scattering, as shown schematically in Fig. d. In this case, part
wave energy reaches points distant from the transmitting antenna by
distance,
5-10 times greater than the geometric visibility range.21
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Rice. Features of propagation of VHF radio waves
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Rice. Long-distance propagation using an "atmospheric waveguide"
22

Irregularities also exist in the ionosphere (uneven concentration
free electrons), where ionospheric wave scattering also occurs. At
high power dissipation ensures communication at distances of 1-2 thousand km.
Other types of long-range UHF and microwave propagation appear when
formation in the atmosphere of extended and clearly defined heterogeneities in
as a layer. The waves propagate inside the layer, reflecting from its boundaries, or
between the ground surface and the lower boundary of the layer. These two cases
are schematically shown in Fig. d. Another type of long-range propagation is reflection from meteor trails. Due to the variability of the meteor process
propagation is used only in special radio communication systems.
In addition to the received radio signal, the receiver is affected by outsiders
vibrations of various origins - radio interference, can cause distortion
received messages: during radiotelephone communication (in the form of clicks, crackling and
noise that impairs the intelligibility of speech messages); telegraph apparatus
prints incorrect characters; on the fax machine form there are extra
lines that spoil the image:
Extraneous radio signals.
Spurious emissions from radio transmitting devices.
Atmospherics.
Industrial interference.
Internal noise of the radio receiver (fluctuation noise).
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Space
noises.

Principles of Radio Communication

Electromagnetic waves
extend to huge
distances, that's why they are used
for transmitting sound (radio waves) and
images (television).
Occurrence condition
electromagnetic wave is
the presence of acceleration in moving
charges!
Radio communication is transmission
information using
electromagnetic waves.

The microphone converts mechanical
oscillations into electromagnetic oscillations
sound frequency.

After modulation, the wave is ready for transmission.
Possessing a high frequency, it can be transmitted to
space.
And it carries audio frequency information.

In the receiver it is necessary to isolate from high-frequency
modulated oscillations of an audio frequency signal, i.e.
carry out detection

Principles of Radio Communication

Converts electromagnetic vibrations into
mechanical vibrations of sound frequency

James Maxwell
English physicist James Clerk
Maxwell developed
electromagnetic theory
fields and predicted
existence
electromagnetic waves.

Heinrich Hertz
In 1887, G. Hertz for the first time
got electromagnetic
waves
and investigated their properties.
He measured the lengths of these
waves and determined the speed
their distribution.

To obtain electromagnetic waves Heinrich Hertz
used a simple device called
Hertz vibrator.
This device is an open
oscillatory circuit.

Electromagnetic waves were recorded from
using a receiving resonator in which
current oscillations are excited.

Alexander Stepanovich Popov
A.S.Popov applied
electromagnetic waves for
radio communications.
Using a coherer, relay,
electric bell Popov
created a device for detecting
and registration of electrical
vibrations - radio receiver.

Popov receiver circuit,

Heinrich Hertz

The principle of radio communication is that
created high frequency electric current,
created in the transmitting antenna, calls in
the surrounding space is rapidly changing
electromagnetic field, which
propagates in the form of electromagnetic
waves.

To produce electromagnetic waves, Heinrich Hertz used a simple device called a Hertz vibrator. This device is

Oscillations
high frequency CARRIER frequency
Fluctuation chart
audio frequency,
those.
MODULATING
fluctuations
Schedule
MODULATED
by amplitude
fluctuations

Electromagnetic waves were recorded using a receiving resonator in which current oscillations were excited.

Detection.

Invention of the radio

Radio communication principle:
In the transmitting antenna it is created
alternating electric current
high frequency, which causes
surrounding space
rapidly changing electromagnetic
field propagating in the form
electromagnetic wave.
Reaching the receiving antenna,
electromagnetic wave causes in it
alternating current of the same frequency, at
which the transmitter operates.

A.S. Popov used electromagnetic waves for radio communication. Using a coherer, a relay, and an electric bell, Popov created a device for detecting

To implement
radio communications
use oscillations
high frequency,
intensively
emitted by the antenna
(produced
generator).
To transmit sound
these high frequency
vibrations change -
modulate with
with help
electrical
fluctuations low
frequencies.
MODULATION –
amplitude change
high frequency
fluctuations
in accordance with
sound frequency.

Popov receiver circuit,

In the receiver of modulated oscillations
high frequencies highlight low frequencies
fluctuations. This process is called
detection.
DETECTION – conversion process
high frequency signal into a low frequency signal.
Received after
signal detection
corresponds to that
sound signal, which
acted on the microphone
transmitter. After
amplification of low vibration
frequencies can be
turned into sound.

The principle of radio communication is that the generated high frequency electric current created in the transmitting antenna causes a

Radio receiver device
Main
element
radio receiver
Popov served
coherer - tube with
electrodes and
metal
sawdust.
Invented by Edouard Branly
in 1891

The simplest radio receiver

Detection.

Transmitting device diagram

Receiver circuit diagram

Application of radio waves
radio waves,
TV,
space communication,
radar.

Radio waves

Radio receiver device

A television

The simplest radio receiver

Space communications

May 7 – RADIO Day

Radar
Detection and
definition
locations
various
objects using
radio waves

Transmitting device diagram

Radar (from the Latin words “radio” to radiate and “lokatio” – location)
Radar – detection and precision
determining the position of objects with
using radio waves.

Receiver circuit diagram

History of radar development
A. S. Popov in 1897 during experiments on radio communication between ships
discovered the phenomenon of reflection of radio waves from the side of the ship. Radio transmitter
was installed on the upper bridge of the transport “Europe”, which was at anchor,
and the radio receiver is on the cruiser Africa. During experiments, when between
cruiser "Lieutenant Ilyin" was hit by ships, instrument interaction
stopped until the ships left the same straight line
In September 1922 in the USA, H. Taylor and L. Young conducted experiments on radio communications on
decameter waves (3-30 MHz) across the Potomac River. At this time, I passed along the river
ship, and the connection was interrupted - which gave them the idea of ​​using
radio waves to detect moving objects.
In 1930, Young and his colleague Highland discovered the reflection of radio waves from
airplane. Soon after these observations they developed a method of using
radio echo for aircraft detection.

Application of radio waves

History of the creation of radar (RADAR - abbreviation for Radio Detection
And Ranging, i.e. radio detection and ranging)
Robert Watson-Watt (1892 - 1973)
Scottish physicist Robert Watson-Watt was the first to build in 1935
radar installation capable of detecting aircraft on
distance 64 km. This system played a huge role in protecting
England from German air raids during World War II
war. In the USSR, the first experiments in radio detection of aircraft
were carried out in 1934. Industrial production of the first radars,
adopted for service, was launched in 1939. (Yu.B.Kobzarev).

Radio waves

Radar is based on the phenomenon of reflection of radio waves from
various objects.
Noticeable reflection is possible from objects if their linear
dimensions exceed the length of the electromagnetic wave. That's why
radars
8
11
operate in the microwave range (10 -10 Hz). As well as the power of the emitted signal
~ω4.

A television

Radar antenna
Antennas in the form of parabolic antennas are used for radar
metal mirrors, in the focus of which the emitting
dipole. Due to the interference of waves, a highly directional
radiation. It can rotate and change the angle of inclination, sending
radio waves in different directions. Same antenna
alternately automatically with the pulse frequency is connected to
transmitter, then to the receiver.

A television:

Space communications

Radar operation
The transmitter produces short pulses of alternating current microwave
(pulse duration 10-6 s, the interval between them is 1000 times longer),
which through the antenna switch enter the antenna and are radiated.
In the intervals between emissions, the antenna receives reflected from the object
signal, while connecting to the receiver input. The receiver performs
amplification and processing of the received signal. In the simplest case
the resulting signal is fed to a beam tube (screen), which shows
image synchronized with antenna movement. Modern radar
includes a computer that processes the signals received by the antenna and
displays them on the screen in the form of digital and text information.

Radar

Determining the distance to an object
ct
S
2
c 3,108 m/s
S – distance to the object,
t – propagation time
radio pulse
to the object and
back
Knowing the orientation of the antenna during target detection, they determine it
coordinates. By changing these coordinates over time, they determine
target speed and calculate its trajectory.

Radar reconnaissance depth
Minimum distance at which a target can be detected (time
propagation of the signal back and forth must
be greater than or equal to the pulse duration)
lmin
c
2
-pulse duration
Maximum distance at which a target can be detected
(the signal propagation time there and back is not
must be longer than the pulse repetition period)
lmax
cT
2
T-period of pulse repetition

Application of radar
Aviation
Based on signals on radar screens, airport dispatchers
control the movement of aircraft along air routes, and pilots
accurately determine flight altitude and terrain contours, can
navigate at night and in difficult weather conditions.

The main application of radar is air defense.
The main task is to observe
by air
space,
discover and lead
purpose, in case
necessity
aim air defense at her
and aviation.

Cruise missile (single launch unmanned aerial vehicle)
launch)
Full control of the rocket in flight
autonomous. The principle of operation of its system
navigation is based on mapping
terrain of a specific area
finding a rocket with reference maps
terrain along its flight route,
pre-stored in memory
onboard control system.
The radio altimeter ensures flight
preset route in mode
bending around the terrain due to precise
maintaining flight altitude: above the sea no more than 20 m, above land - from 50 to 150 m (with
approaching the target - decrease to 20 m).
Correction of the rocket flight path by
marching section is carried out along
satellite navigation subsystem data
and relief correction subsystems
terrain.

The plane is invisible
Stealth technology reduces the likelihood that an aircraft will be
positioned by the enemy. The surface of the aircraft is assembled from
several thousand flat triangles made of
material that absorbs radio waves well. locator beam,
falling on it, dissipates, i.e. the reflected signal is not
returns to the point from where it came (to the radar
enemy stations).

Radar for measuring vehicle speed
One of the important methods for reducing accidents is
control of vehicle speed limits
roads. The first civilian radars to measure
American police traffic speed
were already in use at the end of World War II. Now they
are used in all developed countries.

Radar operation

Weather radars for forecasting
weather. Radar detection objects can
be
clouds,
precipitation,
thunderstorms
foci.
Can
forecast hail, showers, squalls.

Application in space
Radars are used in space research
for flight control
and satellite tracking,
interplanetary
stations,
at
docking
ships.
Radar detection of planets has made it possible to clarify their parameters
(for example, distance from the Earth and rotation speed), state
atmosphere, carry out surface mapping.

Presentation for the lesson “Principles of Radio Communications and Television” Russian scientist A. S. Popov in 1888 predicted the possibility of transmitting signals using electromagnetic waves over long distances. He carried out a practical solution to this problem in 1896, transmitting for the first time in the world a wireless radiogram of two words - Heinrich Hertz - over a distance of 250 m. During these same years, T. Marconi, developing the idea of ​​radio communications, took up the issues of manufacturing radio equipment. In 1897, ahead of the modest A.S. Popov, he received a patent for the possibility of transmitting speech using electromagnetic waves.

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"presentation "Principles of Radio Communications and Television""

Principles of radio communications and television.

Prepared by a physics teacher

Dadyka Oksana Alexandrovna

A little history

The first experimental confirmation of Maxwell's electromagnetic theory was given in the experiments of G. Hertz in 1887.

To produce electromagnetic waves, Hertz used a device consisting of two rods separated by a spark gap. At a certain potential difference, a spark appeared in the gap between them - a high-frequency discharge, current oscillations were excited and an electromagnetic wave was emitted. To receive the waves, Hertz used a resonator - a rectangular circuit with a gap, at the ends of which small copper balls were attached.

• Russian scientist A. S. Popov in 1888 predicted the possibility of transmitting signals using electromagnetic waves over long distances. He carried out a practical solution to this problem in 1896, transmitting for the first time in the world a wireless radiogram of two words - Heinrich Hertz - over a distance of 250 m.

• During these same years, T. Marconi, developing the idea of ​​radio communications, took up the issues of manufacturing radio equipment. In 1897, ahead of the modest A.S. Popov, he received a patent for the possibility of transmitting speech using electromagnetic waves.

A.S. Popov

Radio wave source

• Radio waves are generated when the electric field changes, for example, when an alternating electric current passes through a conductor or when sparks jump through space.

What are radio waves used for?

• The discovery of radio waves has given mankind many opportunities. Among them: radio, television, radars, radio telescopes and wireless communications. All this made our life easier. With the help of radio, people can always ask for help from rescuers, ships and planes can send a distress signal, and you can find out what is happening in the world.

Radio communications during the Great Patriotic War

• From the first days of the Great Patriotic War, radio communications became the most important means of operational command and control of troops and informing the population of a huge country. “From the Soviet Information Bureau” - these words, from June 24, 1941 until the end of the war, opened reports of messages from the front, which thousands of people listened to with excitement every day.

Reliable radio communication is the key to success

• In the first months of the war, the enemy managed to destroy a significant part of our overhead and field cable lines, which led to long interruptions in the operation of wired communications. It became obvious to ensure reliable command and control of troops and their close interaction, especially during battles behind enemy lines and, of course, in aviation, armored forces and the Navy, where radio communications were the only means of communication. During the war, the largest domestic radio factories and research institutes were able to improve and modernize the radio stations in service with the troops and create new, more efficient means of communication.

Modernization of radio stations

During the war, the largest domestic radio factories and research institutes were able to improve and modernize the radio stations in service with the troops and create new, more efficient means of communication. In particular, portable ultra-short wave radio stations were manufactured, intended for rifle and artillery units, the RBM-5 radio station of increased power, economical and reliable, which was also used as a personal radio station for commanders of armies, corps and divisions, several types of special tank radio stations, airborne radio stations troops, various designs of radio receivers.

Radio interference

• The control of German formations and formations was very successfully disrupted by radio interference in January-April 1945 during the East Prussian operation, in which the 131st and 226th special forces radio divisions took an active part. They managed to prevent the enemy from maintaining stable radio communications, although he had 175 radio stations in 30 radio networks and on 300 radio frequencies. In total, reception of about 1200 radiograms was disrupted in the Konigsberg enemy grouping, and 1000 radiograms in the Zemland grouping.

Important role

• Radio communications played an extremely important role in organizing interaction between fronts, armies and formations of various branches of the Soviet Armed Forces when they performed common tasks. In this regard, the organization of radio communications of the Southwestern, Don and Stalingrad fronts in the Stalingrad offensive operation is interesting; Central, Steppe and Voronezh fronts, in the battle of Kursk; 1st Baltic and three Belarusian fronts in the Belarusian strategic operation; 1st, 2nd Belorussian and 1st Ukrainian fronts in the Berlin operation, etc.

And lastly...

The Great Patriotic War largely determined the development of radio-electronic weapons in our army.

Propagation of radio waves.

The ionosphere is the ionized upper part of the atmosphere, starting at a distance of approximately 50-90 km from the earth's surface and turning into interplanetary plasma. The ionosphere is capable of absorbing and reflecting electromagnetic waves. Long and short waves are reflected well from it. Long waves are able to bend around the convex surface of the Earth. Due to multiple reflections from the ionosphere, radio communication on short waves is possible between any points on Earth. VHFs are not reflected by the ionosphere and pass freely through it; They do not go around the Earth's surface, so they provide radio communication only within line of sight. Television broadcasting is only possible in this frequency range. To expand the reception area of ​​television broadcasts, transmitter antennas are installed at the highest possible height; for the same purpose, repeaters are used - special stations that receive signals, amplify them and radiate them further. VHF is capable of providing communication through satellites, as well as communication with spacecraft.